Plaque shows crusting and induration at the periphery and scarring at the center

Lesions persist for years, leading to disfigurement and sometimes skin cancer

Scrofuloderma

Skin lesions result from direct extension of underlying TB infection of lymph nodes, bone or joints

Often associated with TB of the lungs

Firm, painless lesions that eventually ulcerate with a granular base

May heal even without treatment but this takes years and leaves unsightly scars

Miliary TB

Post-primary TB infection that has spread from the primary infection (usually in the lungs) to other organs and secondary reactivation tissues via the bloodstream(Systemic miliary TB occurs when spread is Arterial)

Skin lesions are small (millet-sized) red spots that develop into ulcers and abscesses

More likely in immunocompromised patients, eg HIV, AIDS, cancer

Cryptic type miliary TB usually affects elderly patients

The patient is generally sick

Granulomas are of size 1-2 mm

Choroid tubercles is the pathognomonic finding in miliary TB

Sputum microscopy is usually negative & Montoux test is negative in 20-30%

Tuberculid

Generalisedexanthem in patients with moderate or high degree of immunity to TB because of previous infection

Usually in good health with no identifiable focus of active TB in skin or elsewhere

Erythema induratum (Bazin disease) presents as recurring nodules or lumps on the back of the legs (mostly women) that may ulcerate and scar. It is a type of nodular vasculitis.

Papulonecrotic tuberculid results in crops of recurrent crusted skin papules on knees, elbows, buttocks or lower trunk that heal with scarring after about 6 weeks.

Lichen scrofulosorum is an extending eruption of small follicularpapules characterized by involvement of the sweat glands and hair follicles by causing non caseating epitheloid granulomas in young persons with underlying TB.

DIAGNOSIS:

The diagnosis is usually made or confirmed by characteristic histopathological features on skin biopsy.

Sputum culture (it may take a month or longer for results to be reported)

Chest X-ray and other radiological tests for extrapulmonary infection.

Interferon gamma release assays (IGRA)

Exam Question

Farmer with a single warty lesion on leg may be suggestive of Tuberculosis verrucosa cutis

Tuberculides are seen in Lichen scrofulososum

Lichen scrofulosorum is an extending eruption of small follicularpapules characterized by involvement of the sweat glands and hair follicles by causing non caseating epitheloid granulomas in young persons with underlying TB.